Method and system for image georegistration

ABSTRACT

Image georegistration method and system. An imaging sensor acquires a sensor-image of a scene. Imaging parameters of the acquired sensor-image are obtained, the imaging parameters including at least the detected 3D position and orientation of the imaging sensor when acquiring the sensor-image, as detected using a location measurement unit. A model-image of the scene is generated from a textured 3D geographic model, the model-image representing a texture-based 2D image of the scene as acquired in the 3D model using the imaging parameters. The sensor-image and the model-image are compared and the discrepancies between them determined. An updated 3D position and orientation of the imaging sensor is determined in accordance with the discrepancies. The updated position and orientation may be used to display supplementary content overlaid on the sensor-image in relation to a selected location on the sensor-image, or for determining the geographic location coordinates of a scene element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application filed under 35 U.S.C.§371 of PCT International Application No. PCT/IL2015/050554 with anInternational Filing Date of May 28, 2015, which claims priority toIsrael Patent Application No. 232853, filed on May 28, 2014, the entirecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to georegistration, imageprocessing, and augmented reality.

BACKGROUND OF THE INVENTION

Augmented reality (AR) involves enhancing the perception of a real worldenvironment with supplementary visual and/or audio content, whereartificial information is overlaid onto a view of a physicalenvironment. The supplementary content may be projected onto apersonalized display device, which may be specifically adapted for ARuse, such as a head-mounted display (HMD) or AR-supporting eyeglasses orcontact lenses, or alternatively the display screen of a mobilecomputing device (e.g., a smartphone or tablet computer). Thesupplementary content is typically presented in real-time and in thecontext of elements in the current environment.

AR is increasingly utilized in a wide variety of fields, ranging from:medicine (e.g., enhancing X-ray, ultrasound or endoscopic images of theinterior of a human body to assist therapeutic and diagnosticprocedures); commerce (e.g., allowing a customer to view the inside of apackaged product without opening it); and education (e.g., superimposingrelevant educational material to enhance student comprehension); to:military (e.g., providing combat troops with relevant target informationand indications of potential dangers); entertainment (e.g., augmenting abroadcast of a sporting event or theatre performance); and tourism(e.g., providing relevant information associated with a particularlocation or recreating simulations of historical events). The number andvariety of potential applications for AR continues to expandconsiderably.

In order to associate the supplementary content with the real worldenvironment, an image of the environment captured by a camera or imagesensor may be utilized, as well as telemetric data obtained fromdetectors or measurement systems, such as location or orientationdetermining systems, associated with the camera. A given camera includesvarious optics having particular imaging characteristics, such as theoptical resolution, field of view, and focal length. Thesecharacteristics ultimately influence the parameters of the imagesacquired by that camera, as does the position and viewing angle of thecamera with respect to the imaged scene. The measurement systems areinherently capable of supplying a certain level of accuracy orprecision, but ultimately have limitations arising from the inherentprecision of the various components. Such limitations may also varydepending on the particular environmental conditions (e.g., measurementaccuracy may be lower during nighttime, rain or snow, or inclementweather), and may exacerbate over time due to gradual degradation of theoptics and other system components. As a result, the position andorientation of the camera as acquired via the associated measurementsystems may not correspond exactly to the real or true position andorientation of the camera. Such inaccuracies could be detrimental whenattempting to georegister image data for displaying AR content, as itcan lead to the AR content being superimposed out of context or at anincorrect relative position with respect to the relevant environmentalfeatures or elements.

PCT Patent Application No. WO 2012/004622 to Piraud, entitled “AnAugmented Reality Method and a Corresponding System and Software”, isdirected to an augmented reality method and system for mobile terminalsthat involves overlaying location specific virtual information into thereal images of the camera of the mobile terminal. The virtualinformation and also visual information about the environment at thelocation of the terminal is selected and downloaded from a remotedatabase server, using as well the location (via GPS) and theorientation (via magnetometer, compass and accelerometer) of the mobileterminal. This information is continuously updated by measuring themovement of the mobile terminal and by predicting the real imagecontent. The outline of the captured scene (i.e., crest lines ofmountains in the real camera images) is compared with the outline of aterrain model of the scene at the location of the mobile terminal.

U.S. Patent Application No. 2010/0110069 to Yuan, entitled “System forRendering Virtual See-Through Scenes”, is directed to a system andmethod for displaying an image on a display. A three-dimensionalrepresentation of an image is obtained, and is rendered as atwo-dimensional representation on the display. The location and viewingorientation of a viewer with respect to the display (e.g., the viewer'shead and/or eye position, gaze location) is determined, using an imagingdevice associated with the display. The displayed rendering is modifiedbased upon the determined location and viewing orientation.

U.S. Patent Application No. 2010/0110069 to Ben Tzvi, entitled“Projecting Location Based Elements over a Heads Up Display”, isdirected to a system and method for projecting location based elementsover a heads up display (HUD). A 3D model of the scene within aspecified radius of a vehicle is generated based on a digital mappingsource of the scene. A position of at least one location aware entity(LAE) contained within the scene is associated with a respectiveposition in the 3D model. The LAE from the 3D model is superimposed ontoa transparent screen facing a viewer and associated with the vehicle,the superimposition being in a specified position and in the form of agraphic indicator (e.g., a symbolic representation of the LAE). Thespecified position is calculated based on: the respective position ofthe LAE in the 3D model; the screen's geometrical and opticalproperties; the viewer's viewing angle; the viewer's distance from thescreen; and the vehicle's position and angle within the scene, such thatthe viewer, the graphic indicator, and the LAE are substantially on acommon line.

U.S. Patent Application No. 2013/0050258 to Liu et al., entitled“Portals: Registered Objects as Virtualized Personalized Displays”, isdirected to a see-through head-mounted display (HMD) for providing anaugmented reality image associated with a real-world object, such as apicture frame, wall or billboard. The object is initially identified bya user, for example based on the user gazing at the object for a periodof time, making a gesture such as pointing at the object and/orproviding a verbal command. The location and visual characteristics ofthe object are determined by a front-facing camera of the HMD device,and stored in a record. The user selects from among candidate datastreams, such as a web page, game feed, video, or stocker ticker.Subsequently, when the user is in the location of the object and look atthe object, the HMD device matches the visual characteristics of therecord to identify the data stream, and displays corresponding augmentedreality images registered to the object.

U.S. Patent Application No. 2013/0088577 to Hakkarainen et al., entitled“Mobile Device, Server Arrangement and Method for Augmented RealityApplications”, discloses a mobile device that includes a communicationsinterface, a digital camera, a display and an augmented reality (AR)entity. The

AR entity transmits, via the communications interface, an indication ofthe mobile device location to an external entity. The AR entity obtains,by data transfer from the external entity via the communicationsinterface, a representation determined on the basis of a number of 3Dmodels of one or more virtual elements deemed as visually observablefrom the mobile device location, where the representation forms at leastan approximation of the 3D models, and where the associated sphericalsurface is configured to surround the device location. The AR entityproduces an AR view for visualization on the display based on the cameraview and orientation-wise matching portion, such as 2D images and/orparts thereof, of the representation.

Pritt, Mark D., and LaTourette, Kevin J., “Automated Georegistration ofMotion Imagery”, 40th IEEE Applied Imagery Pattern Recognition Workshop(AIPRW), 2011, discloses techniques for georegistering motion imagerycaptured by aerial photography, based on the registration of actualimages to predicted images from a high-resolution digital elevationmodel (DEM). The predicted image is formed by generating a shadedrendering of the DEM using the Phong reflection model along with shadowscast by the sun, and then projecting the rendering into the image planeof the actual image using the camera model (collinearity equations withradial lens distortion). The initial camera model of the first image isestimated from GPS data and an initial sensor aimpoint. The predictedimage is registered to the actual image by detecting pairs of matchingfeatures using normalized cross correlation. The resulting camera modelforms the initial camera estimate for the next image. An enhancedversion of the algorithm uses two predicted images, where a secondpredicted image consists of the actual image projected into theorthographic frame of the first predicted image.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is thusprovided a method for image georegistration. The method includes theprocedure of acquiring at least one sensor-image of a scene with atleast one imaging sensor. The method further includes the procedure ofobtaining imaging parameters of the acquired sensor-image, the imagingparameters including at least the detected 3D position and orientationof the imaging sensor when acquiring the sensor-image, as detectingusing at least one location measurement unit. The method furtherincludes the procedure of generating at least one model-image of thescene from a textured 3D geographic model, the model-image representinga 2D image of the scene as acquired in the 3D geographic model using theimaging parameters, the model-image including detailed textural imagecontent besides edge features. The method further includes theprocedures of comparing the detailed image content of the sensor-imagewith the detailed image content of the model-image and determining thediscrepancies between them, and determining an updated 3D position andorientation of the imaging sensor in accordance with the discrepanciesbetween the sensor-image and the model-image. The method furtherincludes the procedure of displaying supplementary content overlaid onthe sensor-image, in relation to a selected location on thesensor-image, as determined based on the updated 3D position andorientation of the imaging sensor. The method may further include theprocedure of determining the de the procedure of determining thegeographic location coordinates of a scene element, using the 3Dgeographic model and the updated 3D position and orientation of theimaging sensor. The imaging parameters may further include: the rangefrom the imaging sensor to the scene; the field of view of the imagingsensor; the focal length of the imaging sensor; the optical resolutionof the imaging sensor; the dynamic range of the imaging sensor; thesensitivity of the imaging sensor; the signal-to-noise ratio (SNR) ofthe imaging sensor; and/or lens aberration of the imaging sensor. The 3Dgeographic model may include a street level view of a real-worldenvironment. The method may further include the procedure of updatingthe texture data of the 3D geographic model in accordance with texturedata obtained from the sensor-image. The method may further include theprocedures of: tracking the location of a scene element over a sequenceof image frames of the sensor-image, and displaying supplementarycontent overlaid on at least one image frame of the sequence of imageframes, in relation to the location of the scene element in the imageframe, as determined with respect to a previous image frame of thesequence of image frames. The method may further include the proceduresof: obtaining at least a second set of imaging parameters for at least asecond sensor-image acquired by the imaging-sensor; generating at leasta second model-image of the scene from the 3D geographic model, thesecond model-image representing a 2D image of the scene as acquired inthe 3D geographic model using the second set of imaging parameters;comparing the second sensor-image and the second model image anddetermining the discrepancies between them; determining an updated 3Dposition and orientation of the imaging sensor respective of the secondsensor-image, in accordance with the discrepancies between the secondsensor-image and the second model-image; and displaying supplementarycontent overlaid on the second sensor-image, in relation to a selectedlocation on the second sensor-image, as determined based on the updated3D position and orientation of the imaging sensor respective of thesecond sensor-image. The supplementary content may be displayed on atleast a partially transparent display situated in the field of view of auser, allowing a simultaneous view of the sensor-image presented on thedisplay and of the scene through the display. The method may furtherinclude the procedures of: comparing a new sensor-image with apreviously georegistered sensor-image and determining the discrepanciestherebetween; and determining an updated 3D position and orientation ofthe imaging sensor when acquiring the new sensor-image, in accordancewith the discrepancies between the new sensor-image and the previouslygeoregistered sensor-image.

In accordance with another aspect of the present invention, there isthus provided a system for image georegistration. The system includes atleast one imaging sensor, at least one location measurement unit, atextured 3D geographic model, a processor, and a display. The processoris communicatively coupled with the imaging sensor, with the locationmeasurement unit, with the 3D geographic model, and with the display.The imaging sensor is configured to acquire at least one sensor-image ofa scene. The location measurement unit is configured to detect the 3Dposition and orientation of the imaging sensor when acquiring thesensor-image. The model includes imagery and texture data relating togeographical features and terrain, including artificial features. Theprocessor is configured to obtain imaging parameters of the acquiredsensor-image, the imaging parameters including at least the detected 3Dposition and orientation of the imaging sensor when acquiring thesensor-image as detected using the location measurement unit. Theprocessor is further configured to generate at least one model-image ofthe scene from the 3D geographic model, the model-image representing a2D image of the scene as acquired in the 3D geographic model using theimaging parameters, the model-image including detailed textural imagecontent besides edge features. The processor is further configured tocompare the detailed image content of the sensor-image with the detailedimage content of the model-image and determine the discrepancies betweenthem. The processor is further configured to determine an updated 3Dposition and orientation of the imaging sensor in accordance with thediscrepancies between the sensor-image and the model-image. The displayis configured to display supplementary content overlaid on thesensor-image, in relation to a selected location on the sensor-image, asdetermined based on the updated 3D position and orientation of theimaging sensor. The processor may further be configured to determine thegeographic location coordinates of a scene element, using the 3Dgeographic model and the updated 3D position and orientation of theimaging sensor. The 3D geographic model may include a street level viewof a real-world environment. The processor may further be configured toupdate the texture data of the 3D geographic model in accordance withtexture data obtained from the sensor-image. The location measurementunit may include: a global positioning system (GPS); a compass; aninertial navigation system (INS); an inertial measurement unit (IMU); amotion sensor; a rotational sensor; and/or a rangefinder. The displaymay be at least a partially transparent display situated in the field ofview of a user, allowing a simultaneous view of the sensor-imagepresented on the display and of the scene through the display. Thedisplay may include: a smartphone display screen; a camera displayscreen; a table computer display screen; eyeglasses; goggles; contactlenses; a wearable display device; a camera viewfinder; a head-updisplay (HUD); a head-mounted display (HMD); and/or a transparentdisplay.

In accordance with yet another aspect of the present invention, there isthus provided an image georegistration module. The module is configuredto obtain imaging parameters of at least one sensor-image of a sceneacquired by at least one imaging sensor, the imaging parametersincluding at least the detected 3D position and orientation of theimaging sensor when acquiring the sensor-image as detected using atleast one location measurement unit. The module is further configured togenerate at least one model-image of the scene from a textured 3Dgeographic model, the model including imagery and texture data relatingto geographical features and terrain, including artificial features, themodel-image representing a 2D image of the scene as acquired in the 3Dgeographic model using the imaging parameters. The model-image includesdetailed textural image content besides edge features. The module isfurther configured to compare the detailed image content of thesensor-image with the detailed image content of the model-image anddetermine the discrepancies therebetween, and to determine an updated 3Dposition and orientation of the imaging sensor in accordance with thediscrepancies between the sensor-image and the model-image. The moduleis further configured to display supplementary content overlaid on thesensor-image, in relation to a selected location on the sensor-image, asdetermined based on the updated 3D position and orientation of theimaging sensor. The module may be further configured to determine thegeographic location coordinates of a scene element, based on the updated3D position and orientation of the imaging sensor. The module may befurther configured to update the texture data of the 3D geographicmodel, in accordance with texture data obtained from the sensor-image.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a schematic illustration of a system for imagegeoregistration, constructed and operative in accordance with anembodiment of the present invention;

FIG. 2 is a schematic illustration of an exemplary scene and theresultant images obtained with the system of FIG. 1, operative inaccordance with an embodiment of the present invention;

FIG. 3A is a schematic illustration of exemplary supplementary contentbeing inaccurately superimposed onto a sensor-image, operative inaccordance with an embodiment of the present invention;

FIG. 3B is a schematic illustration of the exemplary supplementarycontent of FIG. 3A being accurately superimposed onto the sensor-image,operative in accordance with an embodiment of the present invention; and

FIG. 4 is a block diagram of a method for image georegistration,operative in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention overcomes the disadvantages of the prior art byproviding a method and system for image georegistration, by utilizing a3D geographic model to compensate for inherent inaccuracies in themeasured parameters of the imaging sensor. The present invention may beused for the presentation of location-based augmented reality, wheresupplementary content is superimposed onto a view of a real-worldenvironment in relation to at least one element in the environment. Themethod involves comparing a sensor image of a scene with a virtual imageas would be acquired within the 3D model using the same parameters asused by the imaging sensor. Based on the deviations between the sensorimage and the virtual image from the 3D model, the measured location(position and orientation) coordinates of the imaging sensor can becorrected to provide more accurate location coordinates. The updatedsensor location can then be used to establish the correct position of anenvironmental element as it appears on the sensor image, in order tocorrectly display augmented reality content in relation to that elementon the image.

Reference is now made to FIG. 1, which is a schematic illustration of asystem for image georegistration, generally referenced 100, constructedand operative in accordance with an embodiment of the present invention.System 100 includes a user device 110 that includes an imaging sensor112, a display 114, a global positioning system (GPS) 116, and a compass118. System 100 further includes a processor 120, a memory 122, and athree-dimensional (3D) geographic model 124. Processor iscommunicatively coupled with user device 110, with memory 122, and with3D model 124.

User device 110 may be situated at a separate location from processor120. For example, processor 120 may be part of a server, such as aremote computer or remote computer system or machine, which isaccessible over a communications medium or network. Alternatively,processor 120 may be integrated within user device 110. If user device110 and processor 120 are remotely located (as shown in FIG. 1), then adata communication channel 130 (e.g., a wireless link) enables datacommunication between processor 120 and the components of user device110. Similarly, processor 120 may be situated at a separate locationfrom 3D model 124, in which case a data communication channel 132 (e.g.,a wireless link) enables data transmission between 3D model 124 andprocessor 120.

User device 110 may be any type of computational device or machinecontaining at least an imaging sensor 112 and position and orientationdetermining components (such as GPS 116 and compass 118). For example,user device 110 may be embodied by: a smartphone, a mobile phone, acamera, a laptop computer, a netbook computer, a tablet computer, ahandheld computer, a personal digital assistant (PDA), a portable mediaplayer, a gaming console, or any combination of the above. It is notedthat display 114 may be integrated within user device 110 (as shown inFIG. 1) or otherwise associated therewith, or alternatively display 114may be part of a separate device that is accessible to and viewable by auser. For example, display 114 may be embodied by: the display screen ofa computational device (e.g., a smartphone display screen, a tabletcomputer display screen, a camera display screen and the like); awearable display device (e.g., goggles, eyeglasses, contact lenses, ahead-mounted display (HMD), and the like); a monitor; a head-up display(HUD); a camera viewfinder; and the like. Display 114 may be at leastpartially transparent, such that the user viewing display 114 cansimultaneously observe images superimposed onto the display togetherwith a view of a physical scene through the display.

Imaging sensor 112 may be any type of device capable of acquiring andstoring an image representation of a real-world scene, including theacquisition of any form of electromagnetic radiation at any range ofwavelengths (e.g., light in the visible or non-visible spectrum,ultraviolet, infrared, radar, microwave, RF, and the like). Imagingsensor 112 is operative to acquire at least one image frame, such as asequence of consecutive image frames representing a video image, whichmay be converted into an electronic signal for subsequent processingand/or transmission. Accordingly, the term “image” as used herein refersto any form of output from an aforementioned image sensor, including anyoptical or digital representation of a scene acquired at any spectralregion.

GPS 116 and compass 118 represent exemplary instruments configured tomeasure, respectively, the position and orientation of user device 110.User device 110 may alternatively include other position and/ororientation measurement instruments, which may be embodied by one ormore devices or units, including but not limited to: an inertialnavigation system (INS); an inertial measurement unit (IMU); motionsensors or rotational sensors (e.g., accelerometers, gyroscopes,magnetometers); a rangefinder; and the like.

Data communication channels 130, 132 may be embodied by any suitablephysical or logical transmission medium operative for conveying aninformation signal between two points, via any type of channel model(digital or analog) and using any transmission protocol or network(e.g., radio, HF, wireless, Bluetooth, cellular, and the like). Userdevice 110 may further include a transceiver (not shown) operative fortransmitting and/or receiving data through communication channel 130.

3D geographic model 124 may be any type of three-dimensionalrepresentation of the Earth or of a particular area, region or territoryof interest. Such a 3D model may include what is known in the art as a:“virtual globe”, “digital elevation model (DEM)”, “digital terrain model(DTM)”, “digital surface model (DSM)”, and the like. 3D model 124generally includes imagery and texture data relating to geographicalfeatures and terrain, including artificial features (e.g., buildings,monuments, and the like), such as the location coordinates of suchfeatures and different views thereof (e.g., acquired via satelliteimagery or aerial photography, and/or street level views). For example,3D model 124 can provide a plurality of visual representations of thegeographical terrain of a region of interest at different positions andviewing angles (e.g., by allowing manipulation operations such aszooming, rotating, tilting, etc). 3D model 124 may include a proprietaryand/or publically accessible model (e.g., via open-source platforms), ormay include a model that is at least partially private or restricted.Some examples of publically available 3D models include: Google Earth™;Google Street View™; NASA World Wind™; Bing Maps™; Apple Maps; and thelike.

The components and devices of system 100 may be based in hardware,software, or combinations thereof. It is appreciated that thefunctionality associated with each of the devices or components ofsystem 100 may be distributed among multiple devices or components,which may reside at a single location or at multiple locations. Forexample, the functionality associated with processor 120 may bedistributed between multiple processing units (such as a dedicated imageprocessor for the image processing functions). System 100 may optionallyinclude and/or be associated with additional components (not shown) forperforming the functions of the disclosed subject matter, such as: auser interface, external memory, storage media, microprocessors,databases, and the like.

Reference is now made to FIG. 2, which is a schematic illustration of anexemplary scene and the resultant images obtained with the system ofFIG. 1, operative in accordance with an embodiment of the presentinvention. A real-world scene 140 of an area of interest is imaged byimaging sensor 112 of user device 110, resulting in image 160. Scene 140includes a plurality of buildings, referenced 142, 144 and 146,respectively, which appear on sensor image 160. While acquiring image160, imaging sensor 112 is situated at a particular position and at aparticular orientation or viewing angle relative to a referencecoordinate frame, indicated by respective position coordinates (X₀, Y₀,Z₀) and viewing angle coordinates (α₀, β₀, λ₀) of imaging sensor 112 inthree-dimensional space (six degrees of freedom). The positioncoordinates and viewing angle coordinates of imaging sensor 112 aredetermined by GPS 116 and compass 118 of user device 110. Imaging sensor112 is further characterized by additional parameters that may influencethe characteristics of the acquired image 160, such as for example:field of view; focal length; optical resolution; dynamic range;sensitivity; signal-to-noise rat(SNR); lens aberrations; and the like.In general, the term “imaging parameters” as used herein encompasses anyparameter or characteristic associated with an imaging sensor that mayinfluence the characteristics of a particular image obtained by thatimaging sensor. Accordingly, sensor-image 160 depicts buildings 142,144, 146 from a certain perspective, which is at least a function of theposition and the orientation (and other relevant imaging parameters) ofimaging sensor 112 during the acquisition of image 160. Sensor-image 160may be converted to a digital signal representation of the capturedscene 140, such as in terms of pixel values, which is then forwarded toprocessor 120. The image representation may also be provided to display114 for displaying the sensor-image 160.

Scene 140 includes at least one target element 143, which is representedfor exemplary purposes by a window of building 142. Target element 143is geolocated at position coordinates (X, Y, Z). As discussedpreviously, imaging sensor 112 is geolocated at position and orientationcoordinates (X₀, Y₀, Z₀; α₀, β₀, λ₀), relative to the same referencecoordinate frame. However, due to inherent limitations in the accuracyof the location measurement components of user device 110 (e.g., as aresult of environmental factors, degradation over time, and/or intrinsiclimits in the degree of precision attainable by mechanical components),the geolocation coordinates of imaging sensor 112 as detected by GPS 116and compass 118 may have certain deviations with respect to the true oractual geolocation coordinates of imaging sensor 112. Thus, the detectedgeolocation of imaging sensor 112 is at deviated position andorientation coordinates (X₀+ΔX, Y₀+ΔY, Z₀+ΔZ; α₀+Δα, β₀+Δβ, λ₀+Δλ). As aresult, if augmented reality content associated with target element 143were to be superimposed onto sensor-image 160 based on the geolocationof target element 143 relative to the detected geolocation of imagingsensor 112, the AR content may appear on image 160 at a differentlocation than that of target element 143, and may thus be confused ormistaken by a viewer as being associated with a different element (e.g.,another object or region of scene 140).

Reference is now made to FIG. 3A, which is a schematic illustration ofexemplary supplementary content being inaccurately superimposed onto asensor-image, operative in accordance with an embodiment of the presentinvention. Sensor-image 160, as viewed through display 114, depictsbuildings 142, 144, 146 at a certain perspective. A reticle 150 is to besuperimposed onto window 143 of building 142, in order to present to theviewer of display 114 relevant information about that window 143 (forexample, to indicate to the viewer that this window 143 represents thewindow of an office that he/she is intending to visit). User device 110assumes the geolocation of imaging sensor 112 to be at deviatedcoordinates (X₀+ΔX, Y₀+ΔY, Z₀+ΔZ; α₀+Δα, β₀+β, λ₀+Δλ), and thereforeassumes window 143 to be located on sensor-image 160 at image planecoordinates (x+Δx, y+Δy, z+Δz), as determined based on the geolocationof window 143 (X, Y, Z) relative to the (deviated) geolocation ofimaging sensor 112, using a suitable camera model. As a result, thereticle 150 is superimposed on sensor-image 160 at image planecoordinates (x+Δx, y+Δy, z+Δz). However, since the true location ofwindow 143 on sensor-image 160 is at image plane coordinates (x, y, z),reticle 150 appears slightly away from window 143 on sensor-image 160.Consequently, the viewer may inadvertently think that reticle 150 isindicating a different window, such as window 141 or window 145, ratherthan window 143. It is appreciated that the present disclosure usescapital letters to denote real-world geolocation coordinates (e.g., X,Y, Z), while using lower case letters to denote image coordinates (e.g.,x, y, 4.

Referring back to FIG. 2, processor 120 obtains a copy of sensor-image160 along with the detected position coordinates (X₀,+ΔX Y₀+ΔY, Z₀+ΔZ)and viewing angle coordinates (α₀+Δα, β₀+β, λ₀+Δλ) of imaging sensor 112(and any other relevant imaging parameters) from user device 110.Processor 120 then proceeds to generate a corresponding image 170 ofscene 140 based on 3D model 124. In particular, processor 120 generatesa virtual image of the real-world representation of scene 140 containedwithin 3D model 124 (e.g., using 3D rendering techniques), where thevirtual image is what would be acquired by a hypothetical imaging sensorusing the imaging parameters associated with sensor-image 160 asobtained from user device 110. The resultant model-image 170 shouldappear quite similar, and perhaps nearly identical, to sensor-image 160since similar imaging parameters are applied to both images 160, 170.For example, the portions of buildings 142, 144, 146 that were visibleon sensor-image 160 are also visible on model-image 170, and appear at asimilar perspective. Nevertheless, there may be certain variations anddiscrepancies between images 160 and 170, arising from the inaccuracy ofthe detected geolocation of imaging sensor 112 by user device 110,relative to its true geolocation, as discussed hereinabove. Inparticular, model-image 170 is based on a (hypothetical) imaging sensorgeolocated at (deviated) coordinates (X₀+ΔX, Y₀+ΔY, Z₀+ΔZ; α₀+α, β₀+β,λ₀+λ) when imaging scene 140, since those are the imaging parametersthat were detected by user device 110, whereas sensor-image 160 is basedon (actual) imaging sensor 112 that was geolocated at (true) coordinates(X₀, Y₀, Z₀; α₀, β₀, λ₀) when imaging scene 140. Consequently, themapping of window 143 on model-image 170 is at image plane coordinates(x′, y′, z′) that are slightly different from the image planecoordinates (x, y, z) of window 143 on sensor-image 160.

Subsequently, processor 120 compares the sensor-image 160 with themodel-image 170, and determines the discrepancies between the two imagesin three-dimensional space or six degrees of freedom (6DoF) (i.e.,encompassing translation and rotation in three perpendicular spatialaxes). In particular, processor 120 may use image registrationtechniques known in the art (e.g., intensity-based or feature-basedregistration), to determine the corresponding locations of common pointsor features in the two images 160, 170. Processor 120 may determine asuitable 3D transform (mapping) that would map model-image 170 ontosensor-image 160 (or vice-versa), which may include linear transforms(i.e., involving rotation, scaling, translation, and other affinetransforms) and/or non-linear transforms.

After the model-image 170 and sensor-image 160 have been compared,processor 120 can then determine the true geolocation of imaging sensor112 based on the discrepancies between the two images 160, 170.Consequently, deviations in the image contents displayed in sensor-image160 arising from the inaccuracy of the detected geolocation of imagingsensor 112 can be corrected, allowing geographically-registered ARcontent to be accurately displayed on sensor-image 160. In particular,processor 120 determines an updated position and orientation of imagingsensor 112, which would result in model-image 170 being mapped ontosensor-image 160 (i.e., such that the image location of a selectednumber of points or features in model-image 170 would substantiallymatch the image location of those corresponding points or features asthey appear in sensor-image 160, or vice-versa). In other words, theupdated geolocation (position and orientation) of imaging sensor 112corresponds to the geolocation of a (hypothetical) imaging sensor thatwould have acquired an updated model-image resulting from the mapping ofmodel-image 170 onto sensor-image 160. The determined updatedgeolocation of imaging sensor 112 should correspond to its actual ortrue geolocation when acquiring sensor-image 160 (i.e., positioncoordinates X₀, Y₀, Z₀; and orientation coordinates α₀, β₀, λ₀).

Supplementary AR content can then be accurately displayed onsensor-image 160 in relation to a selected image location or in relationto the real-world geolocation of an object or feature in scene 140 thatappears on sensor-image 160, in accordance with the updated geolocationof imaging sensor 112. For example, user device 110 identifies at leastone scene element viewable on sensor-image 160, in relation to whichsupplementary AR content is to be displayed. User device 110 determinesthe real-world geolocation of the scene element, and then determines thecorresponding image location of the scene element on sensor-image 160,based on the geolocation of the scene element with respect to theupdated geolocation of imaging sensor 112 (as determined by processor112 from the discrepancies between model-image 170 and sensor-image160). Display 114 then displays the supplementary AR content onsensor-image 160 at the appropriate image location relative to thedetermined image location of the scene element on sensor-image 160. Inthis manner, an “inaccurate” image location of the scene element asinitially determined based on the (inaccurate) detected geolocation ofimaging sensor 112, may be corrected to the “true” image location of thescene element as it actually appears on sensor-image 160, such thatgeographically-registered AR content can be accurately displayed onsensor-image 160 in conformity with the location of the scene element onthe sensor-image. It is appreciated that the term “scene element” asused herein may refer to any point, object, entity, or feature (or agroup of such points, objects, entities or features) that are present inthe sensor-image acquired by the imaging sensor of the presentinvention. Accordingly, the “image location of a scene element” mayrefer to any defined location point associated with such a sceneelement, such as an approximate center of an entity or feature thatappears in the sensor-image.

Reference is now made to FIG. 3B, which is a schematic illustration ofthe exemplary supplementary content of FIG. 3A being accuratelysuperimposed onto the sensor-image, operative in accordance with anembodiment of the present invention. Following the example depicted inFIG. 3A, a reticle 150 is to be superimposed onto window 143 of building142, in order to present relevant information about window 143 to theviewer of display 114. User device 110 initially assumes the geolocationof imaging sensor 112 to be at (deviated) geolocation coordinates(X₀+ΔX, Y₀+ΔY, Z₀+ΔZ; α₀+Δα, β₀+Δβ, λ₀+Δλ), based on which reticle 150would be superimposed at deviated image plane coordinates (x+Δx, y+Δy,z+Δz) on sensor-image 160 (FIG. 3A). Processor 120 determines updatedgeolocation coordinates of imaging sensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀),in accordance with the discrepancies between sensor-image 160 andmodel-image 170. User device 110 then determines updated image planecoordinates of window 143 on sensor-image 160 (x, y, z), based on thereal-world geolocation coordinates of window 143 (X, Y, Z) relative tothe updated real-world geolocation coordinates of imaging sensor 112(X₀, Y₀, Z₀; α₀, β₀, λ₀). Reticle 150 is then superimposed onsensor-image 160 at the updated image plane coordinates (x, y, z), suchthat it appears at the same location as window 143 on sensor-image 160(i.e., at the true image location of window 143). Consequently, theviewer of display 114 sees reticle 150 positioned directly onto window143 of building 142, so that it is clear that the reticle 150 isindicating that particular window 143, rather than a different window inthe vicinity of window 143 (such as windows 141, 145).

It is appreciated that the supplementary AR content projected ontodisplay 114 may be any type of graphical or visual design, including butnot limited to: text; images; illustrations; symbology; geometricdesigns; highlighting; changing or adding the color, shape, or size ofthe image feature (environmental element) in question; and the like.Furthermore, supplementary AR content may include audio information,which may be presented in addition to, or instead of, visualinformation, such as the presentation of video imagery or relevantspeech announcing or elaborating upon features of interest that areviewable in the displayed image.

The operator of user device 110 viewing image 160 on display 114 maydesignate at least one object of interest on image 160, and thenprocessor 120 may display appropriate AR content related to thedesignated object(s) of interest. For example, referring to FIG. 2, theoperator may select building 146 on image 160, such as via a speechcommand or by marking building 146 with a cursor or touch-screeninterface on display 114. In response, processor 120 identifies thedesignated object as representing building 146, determines relevantinformation regarding the designated object, and then projects relevantsupplementary content in relation to that designated object (such as theaddress, a list of occupants or shops residing in that building, and thelike) superimposed onto image 160 viewed on display 114, in conformitywith the location of building 146 as it appears on image 160.

Processor 120 may also use the updated geolocation of imaging sensor 112to extract correct real-world geolocation information relating to scene140, without necessarily projecting supplementary AR content onsensor-image 160. For example, processor 120 may determine thereal-world geolocation coordinates of an object or feature in scene 140,such as the real-world geolocation of window 143, from 3D model 124,based on the determined updated geolocation of imaging sensor 112. Inparticular, processor 120 identifies the updated geolocation coordinatesof imaging sensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀) in 3D model 124, andprojects a vector extending from the imaging sensor coordinates to theobject of interest coordinates within the 3D model, the projectionvector having a length corresponding to the range from the imagingsensor geolocation to the object of interest geolocation (where therange is determined using any suitable means, such as a rangefinder).For example, processor 120 determines the coordinates of a vector in 3Dmodel 124 extending from the updated geolocation coordinates of imagingsensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀) and having a length equal to therange from imaging sensor 112 to window 143, such that the end positionof the vector indicates the geolocation coordinates of window 143 (X, Y,Z).

According to an embodiment of the present invention,geographically-registered supplementary content may be projected onto asequence of displayed images with imaging parameters that change overtime, where the position and orientation of the image contents istracked and the relevant AR content is updated accordingly. For example,referring to FIG. 2, imaging sensor 112 may acquire a second image (notshown) of scene 140, at a different position and viewing angle (e.g.,X₁, Y₁, Z₁; α₁, β₁, λ₁) than that associated with the previous image160. Correspondingly, user device 110 would detect an inaccurategeolocation of imaging sensor 112 during the acquisition of the secondsensor-image (e.g., at deviated coordinates (X₁+ΔX₁, Y₁+ΔY₁, Z₁+ΔZ₁;α₁+Δα₁, β₁+Δβ₁, λ₁+Δλ₁), and would therefore map window 143 on thesecond sensor-image at a second set of deviated image coordinates (e.g.,x+Δx₁, y+Δy₁, z+Δz₁) which differs from the window coordinates in thefirst sensor-image (x, y, z). In order to present correctlygeoregistered AR content associated with window 143 on the secondsensor-image, one approach is to repeat the aforementioned processdescribed for a single image. In particular, processor 120 generates asecond model-image from 3D model 124, the second model-imagerepresenting a virtual image as acquired in 3D model 114 with ahypothetical imaging sensor using the detected imaging parametersassociated with the second model-image. Processor 120 then compares anddetermines discrepancies between the second model-image and the secondsensor-image, and determines the image plane coordinates of window 143on the second sensor-image based on the geolocation of window 143 withrespect to an updated geolocation of imaging sensor 112 as determinedfrom the discrepancies between the second model-image and the secondsensor-image. The relevant supplementary AR content (e.g., reticle 150)is then displayed at the determined image plane coordinates on thesecond sensor-image, such that reticle 150 will be displayed at the sameimage location as window 143 as it actually appears on the secondsensor-image. A second approach is to utilize standard image trackingtechniques to track the location of the scene element between imageframes in order to determine the correct placement for superposition ofthe AR content in subsequent frames, and then intermittently apply theaforementioned process (i.e., determining an updated model-image,comparing with the associated sensor-image, and determining an updatedgeolocation of imaging sensor 112 accordingly) after a selected numberof frames in order to “recalibrate”. An additional approach would be toincorporate predicted values of the imaging sensor geolocation (i.e.,predicting the future location of the operator of user device 110), inaccordance with a suitable prediction model. According to anotherembodiment of the present invention, geographically-registeredsupplementary content may be projected onto multiple displayed images ofthe same (or a similar) scene, acquired by a plurality of imagingsensors, each being associated with respective imaging parameters. Forexample, a plurality of imaging sensors (112A, 1128, 112C) may acquire aplurality of respective sensor-images (160A, 160B, 160C) of scene 140,each sensor-image being associated with at least a respective positionand viewing angle (and other relevant imaging parameters). Thus, window143 of building 142 may appear at a slightly different image location ateach of the respective sensor-images 160A, 160B, 160C. Processor 120generates a set of model-images from 3D model 124, each model-image(170A, 170B, 170C) respective of each of the sensor-images (160A, 160B,160C) based on the associated detected imaging parameters. Subsequently,processor 120 compares between each sensor-image and its respectivemodel-image (170A, 170B, 170C), and determines the discrepancies anddeviations between each pair of images. Processor 120 then determinesthe true geolocation of each imaging sensor (112A, 112B, 112C) for itsrespective sensor-image (160A, 160B, 160C), based on the discrepanciesbetween each sensor-image (160A, 160B, 160C) and its respectivemodel-image (170A, 170B, 170C). A selected image location (e.g.,associated with a scene element) is then determined for eachsensor-image (160A, 160B, 160C) based on the determined real-worldgeolocation of the respective imaging sensor (112A, 112B, 112C), and therespective supplementary AR content is superimposed at the correctgeographically-registered image coordinates on each of the sensor-images(160A, 160B, 160C) presented on a plurality of displays (114A, 114B,110). An example of such a scenario may be a commander of a militarysniper unit who is directing multiple snipers on a battlefield, wherethe commander and each of the snipers are viewing the potential targetat different positions and viewing angles through the sighting device oftheir respective weapons. The commander may then indicate to each of thesnipers the exact position of the desired target with respect to theparticular image being viewed by that sniper, in accordance with thepresent invention. In particular, images of the potential targetacquired by the cameras of each sniper are processed, and a model-imagerespective of each sniper's image is generated using the 3D geographicmodel, based on the detected imaging parameters associated with therespective sniper image. The discrepancies between each model-image andthe respective sniper image are determined, and the geolocation of eachsniper camera for its respective sniper image is determined based onthese discrepancies. Subsequently, an appropriate symbol (such as areticle) can be superimposed onto the sighting device being viewed byeach respective sniper, at the image location of the desired target asit appears on the respective sniper's image.

According to a further embodiment of the present invention, 3Dgeographic model 124 may be updated based on real-time information, suchas information obtained in the acquired sensor-image 160, following theimage georegistration process. In particular, after the updatedgeolocation of imaging sensor 112 has been determined in accordance withthe discrepancies between sensor-image 160 and model-image 170, thetexture data contained within 3D model 124 may be amended to conformwith real-world changes in the relevant geographical features orterrain. For example, processor may identify a discrepancy between aparticular characteristic of a geographical feature as it appears inrecently acquired sensor-image 160 and the corresponding characteristicof the geographical feature as currently defined in 3D model 124, andthen proceed to update 3D model 124 accordingly.

It is appreciated that 3D geographic model 124 may be stored in a remoteserver or database, and may be accessed by processor 120 partially orentirely, as required. For example, processor 120 may retrieve only therelevant portions of 3D model 124 (e.g., only the portions relating tothe particular region or environment where scene 140 is located), andstore the data in a local cache memory for quicker access. Processor 120may also utilize the current geolocation of user device 110 (i.e., asdetected using GPS 116) in order to identify a suitable 3D geographicmodel 124, or section thereof, to retrieve. In other words, alocation-based 3D model 124 may be selected in accordance with thereal-time geolocation of user device 110.

According to yet another embodiment of the present invention,information relating to georegistered images over a period of time maybe stored, and then subsequent image georegistration may be implementedusing the previously georegistered images, rather than using 3D model124 directly. For example, a database (not shown) may store thecollection of sensor-images captured by numerous users of system 100,along with relevant image information and the associated true positionand orientation coordinates as determined in accordance with thediscrepancies between the sensor-image and corresponding model-imagegenerated from 3D model 124. After a sufficient amount of georegisteredsensor-images have been collected, then subsequent iterations ofgeoregistration may bypass 3D model 124 entirely. For example, system100 may identify that a new sensor-image was captured at a similarlocation to a previously georegistered sensor-image (e.g., byidentifying a minimum of common environmental features or imageattributes in both images). System 100 may then determine an updatedposition and orientation for the new sensor-image directly from the(previously determined) position and orientation of the previouslygeoregistered sensor-image at the common location (based on thediscrepancies between the two images), rather than from a model-imagegenerated for the new sensor-image.

Reference is now made to FIG. 4, which is a block diagram of a methodfor image georegistration, operative in accordance with an embodiment ofthe present invention. In procedure 202, a sensor-image of a scene isacquired with an imaging sensor. Referring to FIGS. 1 and 2, imagingsensor 112 acquires an image 160 of scene 140 that includes a pluralityof buildings 142, 144, 146.

In procedure 204, imaging parameters of the acquired sensor-image areobtained, the imaging parameters including at least the detected 3Dposition and orientation of the imaging sensor when acquiring thesensor-image, as detected using as least one location measurement unit.Referring to FIGS. 1 and 2, processor 120 receives imaging parametersassociated with the acquired sensor-image 160 from user device 110. Theimaging parameters includes at least the real-world geolocation(position and orientation) of imaging sensor 112 while acquiringsensor-image 160, as detected via GPS 116 and compass 118 of user device110. The detected geolocation of imaging sensor 112 includes positioncoordinates (X₀+ΔX, Y₀+ΔY, Z₀+ΔZ) and viewing angle coordinates (α₀+Δα,β₀+β, λ₀+λ), which are deviated with respect to the true or actualposition coordinates (X₀, Y₀, Z₀) and orientation coordinates (α₀, β₀,λ₀) of imaging sensor 112 in three-dimensional space (six degrees offreedom).

In procedure 206, a model-image of the scene is generated from a 3Dgeographic model, the model-image representing a 2D image of the sceneas acquired in the 3D model using the obtained imaging parameters.Referring to FIGS. 1 and 2, processor 120 generates a model-image 170 ofscene 140 based on the 3D geographic data contained in 3D model 124. Themodel-image 170 is a virtual image that would be acquired by ahypothetical imaging sensor imaging scene 140 using the imagingparameters obtained from user device 110, where the imaging parametersincludes the detected geolocation of imaging sensor 112 while acquiringsensor-image 160, as detected via GPS 116 and compass 118. Accordingly,the model-image 170 is based on a hypothetical imaging sensor geolocatedat deviated coordinates (X₀+ΔX, Y₀+ΔY, Z₀+ΔZ; α₀+Δα, β₀+Δβ, λ₀+Δλ) whenimaging scene 140. Model-image 170 should depict mostly the sameenvironmental features (i.e., buildings 142, 144, 146) depicted insensor-image 160, but they may be located at slightly different imageplane coordinates in the two images.

In procedure 208, the sensor-image and the model-image is compared, anddiscrepancies between the sensor-image and the model-image aredetermined. Referring to FIGS. 1 and 2, processor 120 comparessensor-image 160 with model-image 170, and determines the deviations ordiscrepancies between the two images 160, 170 in three-dimensional space(six degrees of freedom). Processor 120 may use image registrationtechniques known in the art to determine the corresponding locations ofcommon points or features in the two images 160, 170, and may determinea transform or mapping between the two images 160, 170.

In procedure 210, an updated 3D position and orientation of the imagingsensor is determined in accordance with the discrepancies between thesensor-image and the model-image. Referring to FIG. 2, processor 120determines an updated geolocation of imaging sensor 112 based on thediscrepancies between sensor-image 160 and model-image 170. Inparticular, processor 120 determines an updated position and orientationof imaging sensor 112, such that the image location of a selected numberof points or features in model-image 170 would substantially match theimage location of those corresponding points or features as they appearin sensor-image 160 (or vice-versa). The determined updated geolocationof imaging sensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀) should correspond to itsactual or true geolocation when acquiring sensor-image 160.

In procedure 212, supplementary content is displayed overlaid on thesensor-image in relation to a selected location on the sensor-image, asdetermined based on the updated position and orientation of the imagingsensor. Referring to FIGS. 2 and 3B, user device 110 determines theimage plane coordinates of window 143 on sensor-image 160 (x, y, z),based on the real-world geolocation coordinates of window 143 (X, Y, Z)relative to the updated real-world geolocation coordinates of imagingsensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀). A reticle 150 is superimposed ontosensor-image 160 at the determined image coordinates of window 143 (x,y, z), such that the viewer of display 114 sees reticle 150 positioneddirectly over window 143 on sensor-image 160.

In procedure 214, the geographic location of a scene element isdetermined, using the 3D geographic model and the updated position andorientation of the imaging sensor. Referring to FIGS. 2 and 3B,processor 120 determines the real-world geolocation coordinates ofwindow 143 (X, Y, Z), as indicated by the coordinates of a vector in 3Dmodel 124 extending from the updated geolocation coordinates of imagingsensor 112 (X₀, Y₀, Z₀; α₀, β₀, λ₀) and having a length equal to therange from imaging sensor 112 to window 143. The determined geolocationcoordinates (X, Y, Z) may then be indicated to the viewer if desired,such as being indicated on sensor-image 160 as viewed on display 114.

The present invention is applicable to augmented reality presentationfor any purpose, and may be employed in a wide variety of applications,for projecting any type of graphical imagery or AR content onto areal-world environment in order to modify the viewer's perception ofthat environment. For example, the present invention may be utilized forvarious military objectives, such as for guiding troops, directingweaponry, and providing target information or indications of potentialdangers. Another example is for security related applications, such asfor analyzing surveillance imagery, directing surveillance camerastowards a particular target, or assisting the deployment of securitypersonnel at a crime scene. Yet another potential application is fornavigation, such as providing directions to a specific location at aparticular street or building. Further exemplary applications includeeducation (e.g., such as augmenting an illustration of a particulartopic or concept to enhance student comprehension); entertainment (e.g.,such as by augmenting a broadcast of a sporting event or theatreperformance); and tourism (e.g., such as by providing relevantinformation associated with a particular location or recreatingsimulations of historical events).

While certain embodiments of the disclosed subject matter have beendescribed, so as to enable one of skill in the art to practice thepresent invention, the preceding description is intended to be exemplaryonly. It should not be used to limit the scope of the disclosed subjectmatter, which should be determined by reference to the following claims.

1. A method for image georegistration, the method comprising theprocedures of: acquiring at least one sensor-image of a scene with atleast one imaging sensor; obtaining imaging parameters of the acquiredsensor-image, said imaging parameters comprising at least the detectedthree-dimensional (3D) position and orientation of said imaging sensorwhen acquiring said sensor-image, as detected using at least onelocation measurement unit; generating at least one model-image of saidscene from a textured 3D geographic model, said model-image representinga two-dimensional (2D) image of said scene as acquired in said 3Dgeographic model using said imaging parameters, said model-imagecomprising detailed textural image content besides edge features;comparing the detailed image content of said sensor-image with thedetailed image content of said model-image and determining discrepanciestherebetween; determining an updated 3D position and orientation of saidimaging sensor in accordance with the discrepancies between saidsensor-image and said model-image; and displaying supplementary contentoverlaid on said sensor-image, in relation to a selected location onsaid sensor-image, as determined based on said updated 3D position andorientation of said imaging sensor.
 2. The method of claim 1, furthercomprising the procedure of determining the geographic locationcoordinates of a scene element, using said 3D geographic model and saidupdated 3D position and orientation of said imaging sensor.
 3. Themethod of claim 1, wherein said imaging parameters further comprises atleast one parameter selected from the list consisting of: range fromsaid imaging sensor to said scene; field of view of said imaging sensor;focal length of said imaging sensor; optical resolution of said imagingsensor; dynamic range of said imaging sensor; sensitivity of saidimaging sensor; signal-to-noise ratio (SNR) of said imaging sensor; andlens aberrations of said imaging sensor.
 4. The method of claim 1,wherein said 3D geographic model comprises a street level view of areal-world environment.
 5. The method of claim 1, further comprising theprocedure of updating the texture data of said 3D geographic model, inaccordance with texture data obtained from said sensor-image.
 6. Themethod of claim 1, further comprising the procedures of: tracking thelocation of a scene element over a sequence of image frames of saidsensor-image; and displaying supplementary content overlaid on at leastone image frame of said sequence of image frames, in relation to thelocation of said scene element in said image frame, as determined withrespect to a previous image frame of said sequence of image frames. 7.The method of claim 1, further comprising the procedures of: obtainingat least a second set of imaging parameters for at least a secondsensor-image of said at least one sensor-image acquired by saidimaging-sensor; generating at least a second model-image of said scenefrom said 3D geographic model, said second model-image representing a 2Dimage of said scene as acquired in said 3D geographic model using saidsecond set of imaging parameters; comparing said second sensor-image andsaid second model image and determining the discrepancies therebetween;determining an updated 3D position and orientation of said imagingsensor respective of said second sensor-image, in accordance with thediscrepancies between said second sensor-image and said secondmodel-image; and displaying supplementary content overlaid on saidsecond sensor-image, in relation to a selected location on said secondsensor-image, as determined based on said updated 3D position andorientation of said imaging sensor respective of said secondsensor-image.
 8. The method of claim 1, wherein said supplementarycontent is displayed on at least a partially transparent displaysituated in the field of view of a user, allowing a simultaneous view ofsaid sensor-image presented on said display and of said scene throughsaid display.
 9. The method of claim 1, further comprising theprocedures of: comparing a new sensor-image with a previouslygeoregistered sensor-image and determining the discrepanciestherebetween; and determining an updated 3D position and orientation ofsaid imaging sensor when acquiring said new sensor-image, in accordancewith the discrepancies between said new sensor-image and said previouslygeoregistered sensor-image.
 10. A system for image georegistration, thesystem comprising: at least one imaging sensor, configured to acquire atleast one sensor-image of a scene; at least one location measurementunit, configured to detect the 3D position and orientation of saidimaging sensor when acquiring said sensor-image; a textured 3Dgeographic model of at least said scene, said model including imageryand texture data relating to geographical features and terrain,including artificial features; and a processor, communicatively coupledwith said imaging sensor, with said location measurement unit, and withsaid 3D geographic model, said processor configured to obtain imagingparameters of the acquired sensor-image, said imaging parameterscomprising at least the detected 3D position and orientation of saidimaging sensor when acquiring said sensor-image as detected using saidlocation measurement unit, said processor further configured to generateat least one model-image of said scene from said 3D geographic model,said model-image representing a 2D image of said scene as acquired insaid 3D geographic model using said imaging parameters, said model-imagecomprising detailed textural image content besides edge features, saidprocessor further configured to compare the detailed image content ofsaid sensor-image with the detailed image content of said model-imageand determine discrepancies therebetween, and to determine an updated 3Dposition and orientation of said imaging sensor in accordance with thediscrepancies between said sensor-image and said model-image; and adisplay, communicatively coupled with said processor, said displayconfigured to display supplementary content overlaid on saidsensor-image, in relation to a selected location on said sensor-image,as determined based on said updated 3D position and orientation of saidimaging sensor.
 11. The system of claim 10, wherein said processor isconfigured to determine the geographic location coordinates of a sceneelement, using said 3D geographic model and said updated 3D position andorientation of said imaging sensor.
 12. The system of claim 10, whereinsaid 3D geographic model comprises a street level view of a real-worldenvironment.
 13. The system of claim 10, wherein said processor isconfigured to update the texture data of said 3D geographic model, inaccordance with texture data obtained from said sensor-image.
 14. Thesystem of claim 10, wherein said location measurement unit is selectedfrom the list consisting of: a global positioning system (GPS); acompass; an inertial navigation system (INS); an inertial measurementunit (IMU); a motion sensor; a rotational sensor; and a rangefinder. 15.The system of claim 10, wherein said display comprises at least apartially transparent display situated in the field of view of a user,allowing a simultaneous view of said sensor-image presented on saiddisplay and of said scene through said display.
 16. The system of claim10, wherein said display is selected from the list consisting of: asmartphone display screen; a camera display screen; a tablet computerdisplay screen; eyeglasses; goggles; contact lenses; a wearable displaydevice; a camera viewfinder; a head-up display (HUD); a head-mounteddisplay (HMD); and a transparent display.
 17. An image georegistrationmodule, characterized in that said module is configured to obtainimaging parameters of at least one sensor-image acquired by at least oneimaging-sensor, said imaging parameters comprising at least the detected3D position and orientation of said imaging sensor when acquiring saidsensor-image as detected using at least one location measurement unit;said module being further configured to generate at least onemodel-image of said scene from a textured 3D geographic model, saidmodel including imagery and texture data relating to geographicalfeatures and terrain, including artificial features, said model-imagerepresenting a 2D image of said scene as acquired in said 3D geographicmodel using said imaging parameters, said model-image comprisingdetailed textural image content besides edge features; said module beingfurther configured to compare the detailed image content of saidsensor-image with the detailed image content of said model-image anddetermine discrepancies therebetween, and to determine an updated 3Dposition and orientation of said imaging sensor in accordance with thediscrepancies between said sensor-image and said model-image; and saidmodule configured to display supplementary content overlaid on saidsensor-image, in relation to a selected location on said sensor-image,as determined based on said updated 3D position and orientation of saidimaging sensor.
 18. The module of claim 17, wherein said module isconfigured to determine the geographic location coordinates of a sceneelement, using said 3D geographic model and said updated 3D position andorientation of said imaging sensor.
 19. The module of claim 17, whereinsaid module is configured to update the texture data of said 3Dgeographic model, in accordance with texture data obtained from saidsensor-image.